[bab62]

My battery can't hold a charge when the car sits for over 3 days, such as at a campground or at the airport. I'd like to get a better battery. What might be the best battery I could get for this hyped-up-with-computerized-systems car?

The first thing you need to do is find out if the battery and alternator are doing their job. Don't wait, take it to the nearest auto parts store and have them test the battery and alternator. Why would you wait a week for the dealership appointment?
If the battery and alternator are good, then keep the dealership appointment, or better find a local auto repair shop that specializes in electrical problems.

Take the logical approach by starting with the diagnosis of the battery and alternator, then move ahead based on those findings.